what tests can i do, if any, and what do i look for when im buying a box thats no longer in the car without dissassembling totally

the best thing it to removed the bell housing , have a look at the pinion & crown wheel .

Most vw motors dont have the HP to brake these parts , but if it was behind a V8 or rota , subaru !

If you getting it form one of the lads on this fourm , have a look at the number of posts they have & just who they are .

I have never had problems with buying any thing from any one on here

seagull

theres not much you do do except pull the drain plugs and see how much metal is on the magnetic plugs and if the oil is dirty black although this may not indicate problems

Also try and select gears etc and reverse etc

Grab the axles and see if theres excessive end play in the diff

otherwise but and fit and ask for a guarentee